Pizza can be made
awesome with very little effort. I went through a major pizza kick about a month into my weight loss and dropped eight pounds that month, so I can attest to the magnificence of a good pizza.
If you want a super-skinny pizza or are watching carbs, follow the great suggestions here to use a Flat-Out wrap or tortilla as the crust. If you're counting calories and aren't carb-sensitive, buy a pre-fab thin crust (I think Boboli makes some, though I haven't looked) or make your own thin-crust dough recipe (this is what I do).
You can save a few calories on the sauce if you make sure to buy a product with no sugar added or make your own.
I use real cheese because fake cheese makes me genuinely sad. Weigh your cheese out because it's likely the most caloric thing on your pizza aside from the crust itself. Whoever suggested using strongly flavored cheese more sparingly instead of a whole lot of bland, blah cheese is right--a couple of pinches of mozzarella and some grated parmigiano reggiano is WAY better than a layer of plastic goo.
Use veggies. LOTS of veggies. Cover your pizza with them. They'll fill you, they'll nourish you, and they'll taste good. There's no excuse for a veggie-less pizza.